1HD-T experts needed! - now with Amazon rewards!! (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Jan 8, 2011
Threads
20
Messages
164
Location
Victoria, BC
I was posting about a brake vacuum problem over in the 80 thread but figured Might get some traction here.

Does anyone with a 1hdt and gear driven vacuum pump know how fast the vacuum is supposed to build? Mine appears to be slow and I don't know why.

I have rebuilt the vacuum pump, new aisin master,.new soft lines and now a new Bosch brake booster. It still seems to build vacuum slowly but I can find a baseline rate anywhere online.
Here is the other thread with videos
 
Two more thoughts are in my head right now.
1. That build rate looks slow but is normal. (However I can trigger the low pressure light after three fast pedal pumps with engine running).
2. Since the pump vents into the engine it could be clogged in the engine? I doubt this is possible but also don't know where that air goes once it exits the front of the gear pump
 
recommend plugging all vacuum source to the pump (e.g., brake booster) and put a vacuum gauge on one of the ports to see if it is still slow. If it is, pump is worn out. If quick, you have a pretty good vac leak. Are your brakes acting up?
 
Yeah I ran the guage right on the pump and it spiked right away but that's also because there was no volume attached to it. I then connected the pump right into the booster without the reservoir and it was slow to build again on the old booster. Havnt tried it on the new one but suspect the same as there is no difference with them all hooked up. Also I can let the truck sit for hours and when I pop the soft lines off I can hear the pop of the vacuum it's holding.

Could it be that I have so much piston blow by that it's putting too much pressure into the engine which is effecting the vacuum pump?
 
recommend plugging all vacuum source to the pump (e.g., brake booster) and put a vacuum gauge on one of the ports to see if it is still slow. If it is, pump is worn out. If quick, you have a pretty good vac leak. Are your brakes acting up?
Brakes don't seem to slow me down as good as it should. I can only seem to lock up one tire when the abs is disconnected. It seems ok for daily driving but after a few rapid brake pumps I can notice a loss in brake power. Also I don't remember being able to trigger the brake light when pumping the brakes three times at idle.
 
May wanna read this

 
May wanna read this

Yeah this is what got me started on the pump rebuild but it looked mint when I had it apart. I ended up replacing the vanes anyway with new bearings and seals.

Maybe I'm chasing a ghost but I have no baseline for build speed which is driving me crazy
 
Both my diesel cruisers had vacuum immediately anytime I got in the car to drive it.
Not sure if that's because the reservoir is holding vacuum, or the pump provides vacuum immediately
Any chance you would be able to put a gauge onto your vacuum system and send a video?
 
If there's a leak in the system then you'll likely have a hard brake pedal after the truck sits for a while.
 
If anyone has this engine/truck could someone hook up a vacuum line to show me what a normal vacuum build speed is? Seems to literally be an impossible thing to find on the internet
 
I can hook up a vacuum gauge on my brother's HDJ81, but it might be a couple of weeks since I'm currently 300 miles away.
 
How confident are you in the pump rebuild? I haven't rebuilt a 1hdt/hz pump but (going by some old memory) when i rebuilt my 2h pump a common error was putting the vanes in backwards.
Very but will take it apart again if nothing else makes sense. I paid special attention to vane installation and it seemed like something that was hard to get wrong (famous last words)
 
@Rubiclone I had this same issue, ended up being a blockage in one of the lines. Rig up compressed air on the line that connects to the vac pump and see how it is coming out by the booster. Also make sure you are using vacuum rated rubber lines, you might have one that is collapsing under vacuum. Start with changing them all to new lines to rule that out.
 

Users who are viewing this thread

Back
Top Bottom